Olfactory receptor neurons are faced with the daunting task of distinguishing between hundreds to thousands of odor molecules. It is well known that single olfactory receptors neurons can respond to more than one odor and that mixtures of odors elicit responses that are often different from the summation of the individual odor responses. The unpredictability of odor mixture response suggests that interactions occurring at some level of the transduction pathway enhance or suppress the odor signal. When mixture interactions occur between second messenger and messengers and receptors, electrogenic exchanges or effector channels, the interactions are referred to as cross-talk. We hypothesize that cross-talk during odor transduction plays an important role in olfactory coding of odor mixtures by making the responses of single ORNs unpredictable. In the first Specific Aim, we will use perforated patch recordings, Ca2+ imaging and activity dependent labeling techniques to identify the odor responsivity profiles of specific morphological subtypes of squid olfactory receptor neurons. In Specific Aim 2, perforated-patch voltage-clamp and Ca2+ and Ca2+ imaging techniques will be used to categorize the interactions occurring in response to specific binary odor mixtures. Components of the binary mixtures to be tested are identified in Aim 1. In Specific Aim 3, we will investigate the transduction mechanism that underlie the mixture interactions identified in Specific Aim 2. The work in this aim represents the first attempt to determine mechanisms of cross-talk at the level of isolated voltage-clamped olfactory receptor neurons and will greatly advance our understanding of how single cells encode odor mixtures.